World number two Maria Sharapova suffered a shock defeat at the hands of Flavia Pennetta, losing in three sets to the defending champion during the BNP Paribas Open.
In a contest lasting two hours and eight minutes, the 27-year-old Russian lost nine of the last 12 games against the number 15 seed. Taking place in California, Sharapova edged the first set before losing 2-6 6-3 6-2.
The 33-year-old Italian, who also won the 2011 Australian Open doubles tournament, took advantage of incompetent mistakes from Sharapova, a former world number one.
11 double faults from the five-time grand slam winner, combined with 42 unforced errors, saw Sharapova humiliated by Pennetta having previously beaten Victoria Azarenka 6-3 6-2 earlier in the day. Coolly seeing off the world number 32, her fourth round opponent also breezed past the third round with a 6-4 6-2 victory over Australian Samantha Stosur, seeded 21 in the world.
Sharapova commented on her performance, saying: "Maybe I wasn't playing my best tennis but I was competitive enough. I just wasn't able to step up in the key moments."
Pennetta will now face number 24 seed Sabine Lisicki, who reached the Wimbledon final in 2013. The German edged Caroline Garcia of France 6-4 6-4 in the fourth round, after impressing against world number 11 Sara Errani with a 6-4 6-2 dominant performance.
Another shock came in the form of world number 85 Lesia Tsurenko, who overcame world number six Eugenie Bouchard in a marathon falling just 11 minutes short of three hours – despite losing the first set. The Ukrainian won 6-7 (5-7) 7-5 6-4 after recovering from 1-4 down in the final set, during which Bouchard dropped her serve three times in a row.
Sharapova was previously named as the 2012 ESPY Best Female Tennis Player.